ILOILO, Philippines -- Bowls of piping hot barracuda soup were the much-anticipated treat when the Roa family gathered for a casual and relaxing Sunday meal.

Within hours, all six fell deathly ill. So did two dozen others from the same neighborhood. Some complained of body-wide numbness. Others had weakness in their legs. Several couldn't speak or even open their mouths.

"I was scared. I really thought I was going to die," said Dabby Roa, 21, a student who suffered numbness in his head, tingling in his hands and had trouble breathing.

What Roa and the others suffered that night last August was ciguatera poisoning, a rarely fatal but growing menace from eating exotic fish. All had bought portions of the same barracuda from a local vendor.

Experts estimate that up to 50,000 people worldwide suffer ciguatera poisoning each year, with more than 90 percent of cases unreported. Scientists say the risks are getting worse, because of damage that pollution and global warming are inflicting on the coral reefs where many fish species feed.

Dozens of popular fish types, including grouper and barracuda, live near reefs. They accumulate the toxic chemical in their bodies from eating smaller fish that graze on the poisonous algae. When oceans are warmed by the greenhouse effect and fouled by toxic runoff, coral reefs are damaged and poison algae thrives, scientists say.

"Worldwide, we have a much bigger problem with toxins from algae in seafood than we had 20 or 30 years ago," said Donald M. Anderson, director of the Coastal Ocean Institute at the Woods Hole Oceanographic Institution in Massachusetts.

"We have more toxins, more species of algae producing the toxins and more areas affected around the world," he said.

Although risk of ciguatera has soared recently, the phenomenon is ancient. Fish poisoning shows up in Homer's Odyssey. Alexander the Great forbade his armies to eat fish for fear of being stricken, according to University of Hawaii professor Yoshitsugi Hokama.

Capt. James Cook and his crew probably suffered ciguatera poisoning in 1774 after eating fish near Vanuatu in the South Pacific, according to crew journals and correspondence studied by Dr. Michael Doherty of the Swedish Epilepsy Center in Seattle, writing in the scientific review Neurology. Cook recorded that they "were seized with an extraordinary weakness in all our limbs attended with a numbness or sensation like ... that ... caused by exposing one's hands or feet to a fire after having been pinched much by frost."

Ciguatera has long been known in the South Pacific, the Caribbean and warmer areas of the Indian Ocean. Some South Pacific islanders use dogs to test fish before they eat.

But in the past decade, it has spread through Asia, Europe and the United States, where more restaurants are serving reef fish, prized for their fresh taste and exotic cachet.

In the United States, ciguatera poisonings are most frequent in Florida, Texas and Hawaii, which has seen a fivefold increase since the 1970s to more than 250 a year.

Hong Kong, which imports much of its seafood, went from fewer than 10 cases annually in the 1980s to a few hundred now.

Still, Hong Kong diners pay a premium for the risky fish. Rare species like the Napoleon wrasse fetch nearly $50 a pound. The fish are increasingly shipped live from Southeast Asia and as far away as the South Pacific, raising concerns from the World Conservation Union that many species, especially groupers, could be fished out of existence.

Professor Yvonne Sadovy, of the University of Hong Kong, predicted that high demand and cash-hungry fishermen mean that "ciguatoxic fish entering markets around the world is going to increase."

Should global warming and pollution worsen and boost ciguatera poisonings, as most experts predict, health officials will face a daunting challenge.

Currently, there is no reliable way to detect whether a fish has ciguatera. The molecule is extremely complex and differs markedly from region to region.

There also is no antidote.

Furthermore, doctors are often ill-equipped to diagnose ciguatera, which has a range of symptoms and is sometimes misdiagnosed as chronic fatigue syndrome or other maladies.

Those challenges faced Dr. Edgar Portigo at Doctors General Hospital in Iloilo, about 265 miles southeast of Manila, when the Roa family and others arrived. The emergency room was filling with patients yelping in pain, vomiting, or, in the case of Dabby Roa, so paralyzed that he had to be carried in by a security guard.

"Normally, you have one or two emergency cases. Here we had 30 plus all at once," from ages 4 to 65, Portigo said.

At first, Portigo surmised the patients had heavy metal poisoning. But when he learned of the common thread -- the barracuda dinners -- he sent a sample of the fish to Manila for testing. It came back positive for ciguatera.

Portigo gave his patients intravenous drips and a diuretic to relieve their suffering. Most like Roa were released from the hospital in a week, he said, and fully recovered.

"Although this is quite rare, it can happen anytime," said Portigo, noting this was the first ciguatera outbreak in the city.

A relatively quick recovery is the norm, but some have lingering symptoms.

Dennis McGillicuddy, a 65-year-old retired cable television company owner from Sarasota, Fla., fell sick a few hours after eating a mutton snapper he caught off the coast of Bermuda in 2000. Within hours, his vomiting and diarrhea were so severe that he became delirious and was "reduced to crawling," he recalled.

The digestive symptoms lasted two weeks. After that, McGillicuddy became so sensitive to temperature extremes that it was hard to take a shower. Numbness in his extremities lasted for almost a year.

"I've never had anything like this," said McGillicuddy, who still occasionally feels tingling in his left arm. "You feel terrible all over your body."

The U.S. Food and Drug Administration and others who monitor ciguatera say they are hampered by the lack of a reliable test. Bans on certain fish or "hot spots" can help, but they often are impractical.

"It's very hard to manage," said professor Richard Lewis, of the University of Queensland in Australia, who has studied ciguatera. "Unless you don't eat the fish, you have a risk of getting ciguatera."

Poorer countries often lack even rudimentary measures to protect consumers. Those precautions that do exist are undermined by government corruption or lack of enforcement.

Hong Kong has refused to enact mandatory measures to prevent ciguatera despite increased outbreaks. It argues that educating consumers and traders is the answer, rejecting calls to crack down on traders or ban fish from suspect areas.

"Given the fact we eat so much seafood in Hong Kong, this should be one of the priorities in protecting the population," Sadovy said. "I just hope we don't have to wait for someone to die before something is done."

In Iloilo, fear has done what the Philippine government has not. Consumers stopped buying barracuda after the ciguatera outbreak. Vendors have switched to less risky varieties.